At present, a typical network of voice store-and-forward messaging system sites utilizes a network addressing plan to provide a network address for users. For example, a message sender uses the network address of a message recipient whenever the message sender sends a message to the message recipient. In addition, the network of voice store-and-forward messaging system sites typically provides the network address of the message sender to the message recipient, for example, by announcement, whenever the message recipient receives the message.
In practice, a network of voice store-and-forward messaging system sites is typically used as an adjunct to a telephone network. At present, in such an arrangement, it is not unusual to find that the network address of the message recipient in the network of voice store-and-forward messaging systems is different from the telephone number of the message recipient.
In a ROLM.TM. PhoneMail.TM. network of voice store-and-forward messaging systems manufactured by ROLM Systems of Santa Clara, Calif., two separate network addressing plans have been used, namely, a Location Prefix Plan and a Uniform Addressing Plan. In the Location Prefix Plan, each site in the network is required to define one or more "Location Prefixes," also known as "Location Codes," that uniquely identify a site. Further, in accordance with this plan, the prefixes for every site in the network must have the same length, typically 1-3 digits. In addition, one "Network Identifier," typically one digit, is selected for the whole network to signify a network address--a common choice is the digit "8", and subscriber mailbox addresses for sites in the network may not use this digit as their initial digit. Still further, local extensions and subscriber mailbox addresses for a site must have the same length, typically 3-5 digits, however, the length may vary from site to site over the network.
In the Uniform Addressing Plan, each site in the network is required to define one or more network address extension ranges of the form abcxxx where "a", "b", and "c" are predetermined digits and "x" are digits from 0 to 9. Further, all network address extension ranges in the network must have the same length. Still further, subscriber mailbox addresses for a site must have the same length, however, the length may vary from site to site over the network.
Although the above-described addressing plans work well in certain limited environments, more complex environments are not adequately served by either of them. In particular, a major drawback of the Location Prefix Plan is that all network addresses in the network must begin with the same digit and all location prefixes in the network must have the same length. Further, a major drawback of the Uniform Addressing Plan is that all network addresses in the network must have the same length. Still further, both plans share the following drawbacks: (a) all subscriber mailbox addresses at a site must have the same length and (b) no overlapping of addresses is allowed when specifying either extension ranges or location prefixes.
These drawbacks become apparent when one wishes to "mirror" the telephone numbers of users in a telephone network with the network addresses of users in a network of voice store-and-forward messaging system sites. The term "mirror" means that a message sender can utilize the telephone number of a message recipient as the network address of the message recipient in the network of voice store-and-forward messaging system sites. As one can readily appreciate such a mirroring of telephone numbers in the network addressing plan is advantageous because users would only have to remember one telephone number to place calls over the telephone network and to send messages over the network of voice store-and-forward messaging system sites.
The above-described drawbacks are readily apparent in the following environments: (a) networks of store-and-forward messaging system sites which use public as well as private telephone network facilities and (b) networks comprised of two or more of the following types of sites: (i) collocated sites, i.e., sites located in the same building; (ii) sites in the same area code; (iii) sites located in different area codes, and (iv) international sites.
Some of the above-described drawbacks can be understood in the context of a few simple examples. First, assume that a telephone network comprises public as well as private facilities. In such a telephone network, callers may dial 8-prf-xxxx to telephone called parties at other sites which are connected vi private tie-lines ("prf" refers to a three-digit prefix) whereas callers have to dial seven digits or ten digits--depending on whether the called party is in the same or a different area code, respectively--to utilize the public switched telephone network. This telephone network dialing plan cannot be mirrored in a network of voice store-and-forward messaging system sites by using the Location Prefix Plan or the Uniform Addressing Plan. Second, assume that a telephone network is comprised of only the public switched telephone network and that it comprises multiple sites in the same area codes, sites in different area codes, and even sites in different countries. When a caller places a telephone call, he or she may dial 7, 10, or more than 10 digits--for international calls--depending on the destinations of the calls. Again, this telephone dialing plan cannot be mirrored in a network of voice store-and-forward messaging system sites by using the Location Prefix Plan or the Uniform Addressing Plan.
Attempts in the art to overcome the above-described drawbacks have entailed the use of complicated numbering plans. This has resulted in a new drawback because it has required message system users to use complicated, hard-to-remember sequences of digits to transmit messages.
In light of the above, there is a need in the art for a method and apparatus for providing a universal addressing plan for use in a network of store-and-forward messaging system sites which provides a capability whereby any complex telephone numbering plan can be mirrored among the sites in the network, notwithstanding whether the sites utilize the public switched network or a private network. Further, this capability should include networks which are comprised of: collocated sites; sites located in the same area code; sites located in different area codes; and international sites. Still further, there is a need for method and apparatus for providing such a universal addressing plan wherein network address portability is provided so that a user can retain the same network address whenever he or she moves from one site to another site.